Viridans streptococci and the β-hemolytic streptococci constitute a diverse group of organisms with varying environmental niches and pathogenicity. Although these organisms reside as commensals in the respiratory and intestinal tracts of humans, they may also invade sterile body sites, resulting in life-threatening diseases.
Viridans streptococci such as S. mitis group consisting of S. mitis, S. sanguis, S. gordonii, S. oralis are an important part of the normal microbial flora of humans. They are indigenous to the upper respiratory tract, the female genital tract, and all regions of the gastrointestinal tract, but are most prevalent in the oral cavity. They are responsible for bacteremia with 2.6% of positive blood cultures reported from clinical laboratories, for meningitis accounting for 0.3% to 5% of culture-proven cases, for pneumonia even if often isolated with non clinical significance, and miscellaneous infections such as pericarditis, peritonitis, acute bacterial sialadenitis, orofacial odontogenic infections, endophtalmitis, spondylodiscitis, and various upper respiratory tract infections (otitis, media, sinusitis).
Beta-hemolytic streptococci of large colony size (0.5 mm in diameter) can be grouped with Lancefield antisera using latex agglutination or coagglutination directed against the cell wall carbohydrate of groups A, B, C, or G. Infections caused by these groups are often severe: pneumonia, pharyngitis, arthritis with 11% to 28% of cases, osteomyelitis, endocarditis, respiratory tract infections, endocarditis, meningitis, puerperal infection, neonatal sepsis, bacteremia, skin and soft tissue infections (cellulitis, foot ulcers, abscess), infections of the female genital tract (group B streptococci) and other miscallenous infections such as pericarditis, pyomyositis, purpura, and spinal epidural abscess (Mandell, Douglas and Bennett's: Principles and practice of infectious Disesases, Sixth ed., volume 1).
Because enterococci are part of the normal gut flora of almost all humans, they are capable of causing infections both in and out of the hospital setting. Most enterococcal infections, however, occur in hospitalized patients or patients undergoing therapy such as peritoneal or hemodyalisis. Currently, enteroccocci infections rank second or third in frequency as causes of nosocomial infections in the United-States. Risk factors for acquiring nosocomial enterococcal infections include gastrointestinal colonization; serious underlying disease; a long hospital stay; prior surgery; renal insufficiency; neutropenia; transplantation (especially liver and bone marrow), the presence of urinary or vascular catheters; and residency in an intensive care unit. Clinical infections caused by enterococci are urinary tract infections, bacteremia, endocarditis, intra-abdominal and pelvic infections, wound and tissue infections, meningitis, respiratory tract infections and neonatal sepsis (Mandell, Douglas and Bennett's: Principles and practice of infectious Disesases, Sixth ed., volume 1).
Peptostreptococcus species are commensal organisms in humans, living predominantly in the mouth, skin, gastrointestinal, and urinary tracts, and compose a portion of the bacterial gut flora. Under immunosuppressed or traumatic conditions these organisms can become pathogenic, as well as septicemic, harming their host. Peptostreptococcus can cause brain, liver, breast, and lung abscesses, as well as generalized necrotizing soft tissue infections. They participate in mixed anaerobic infections, a term which is used to describe infections that are caused by multiple bacteria. These different bacterial species raise the problem of their detection in human pathological specimens and of their identification when isolated from such samples (Mandell, Douglas and Bennett's: Principles and practice of infectious Disesases, Sixth ed., volume 1).
Patients receiving total joint replacements number in the hundreds of thousands each year worldwide, and millions people have indwelling prosthetic articulations. Between 1 and 5% of indwelling prostheses become infected; this is a calamity for the patient, and it is associated with significant morbidity and occasionally with death. Prosthesis removal, which usually is necessary to treat these infections, produces large skeletal defects, shortening of the extremity, and severe functional impairment. The health cost of treating a single septic prosthetic joint has been conservatively at $50,000 to $60000, with an extrapolated expenditure of more than $200 million to $250 million per year in the United States alone. The patient faces protracted hospitalization, sizable financial expense, and potentially renewed disability (Mandell, Douglas and Bennett's: Principles and practice of infectious Disesases, Sixth ed., volume 2).
Prosthetic joints become infected by two different pathogenetic routes: locally introduced and hematogenous types of osteomyelitis. The locally introduced form of infection is the result of wound sepsis contiguous to the prosthesis or operative contamination. Any bacteremia can induce infection of a total joint replacement by the hematogenous route. Dentogingival infections and manipulations are known causes of Viridans streptococcal and anaerobic Peptostreptococcus infections in prosthesis. Pyogenic skins processes can cause staphylococcal and streptococcal (groups A, B, C and G streptococci) infections in joint replacements. Genitourinary and gastrointestinal tract procedures or infections are associated with gram-negative bacillary, Enterococci and anaeobic infections of prostheses. The frequency of the presence of the specific etiologic microorganisms in prosthetic joint sepsis varies among the published studies, but a general view of the spectrum of this bacteriology and the prominence of certain microbial groups is known. Staphylococci (coagulase-negative staphylococci and S. aureus) are the principal causative agents; aerobic streptococci and gram-negative bacilli are each responsible for 20% to 25%, and anaerobes represent 10% of these infections. The spectrum of microbial agents capable of causing prosthetic joint infection is unlimited and included organisms ordinarily considered “contaminants” of cultures, such as Bacillus spp. Although infections with fungi (particularly Candida) and mycobacteria are rare, these infections have been described (Mandell, Douglas and Bennett's: Principles and practice of infectious Diseases, Sixth ed., volume 2).
The gold standard for diagnosing prosthesis infection remains bacteriological analysis, which involved isolation and culture of the infecting bacteria at the site of infection, from relevant samples. Bacteriological analysis is generally considered as significant if at least 2 samples taken during the surgery are positive for streptococci, enterococci and Peptostreptococcus spp. Ultrasound-guided needle aspiration or image-guided core-needle biopsy can also be carried. Several drawbacks are however associated to bacteriological analysis. Conventional detection methods rely on the evidencing of Gram-positive bacteria on direct examination of the pathological specimen. However the microscopic detection of bacteria of the genus Streptococcus and related genera in clinical specimens has a limited sensitivity. It is therefore possible that a pathological specimen is not detected by direct microscopic examination of this pathological specimen. In addition, even though their structure is of Gram-positive bacteria type, they may give a false Gram-negative result after Gram staining of the pathological sample and give rise to erroneous or inconclusive identification. When a bacterium of one of the species of the genera under consideration is isolated in the laboratory, conventional phenotype identification methods are the most commonly used to identify bacteria of species belonging to genus Streptococcus and related genera, and several identification kits and automated analyzers have been developed to assist phenotype identification of bacteria of genus Streptococcus and related genera. In this respect, the extent of identification in routine practice is variable. In particular, one of the tests used for identifying streptococci and bacteria of related genera is the detection of a haemolytic reaction, i.e. the destruction by the bacterium of red blood cells contained in a blood agar. However, this haemolytic reaction can be inhibited by the presence of oxygen or by the presence of peroxide when streptococci bacteria are cultured in the presence of a high carbon dioxide concentration. Moreover, it is recognized that there exists a certain extent of subjectivity in assessing haemolysis by colonies of streptococci and hence inter-operator variability which is detrimental to the quality of identification of these.
There are currently no other methods for establishing the diagnosis of streptocococci, enterococci and Peptostreptotoccus spp. prosthesis infection. Thus the object of this invention proposes an alternative technique for the diagnosis of these infections. A serological approach based on the antibodies of anti-streptococci, anti-enterococci and anti-Peptostreptococcus spp. could overcome the drawbacks associated to bacteriological analysis.